Using Iridium, which is six times harder and eight times stronger than platinum, the tip can be shrunk to only 0.4mm. This means the voltage requirements are decreased while firing performance is greatly improved. A U-Groove has been cut inside the ground electrode to maintain the large volume of space required to form the nucleus of a flame. While still keeping the required voltage low, this technology enables excellent firing performance without increasing the spark gap. The tip of the ground electrode has been cut to form a taper. This greatly improves firing performance by reducing quenching. The extreme hardness and high melting point of Iridium prevented the use of this incredible metal until Denso perfected the Laser Welding Process, which provides a 360° seal so reliable the electrode resists wear even in the harshest conditions.